I was referred by a friend, then given a coding challenge which I did well but not perfect in. Then there was a phone call with a brief conversation (why Palantir, what are you looking for in an internship, etc.) with a coding challenge. Heard back a few days later to schedule an on-site interview in a few weeks. During the on-site, I had 3 technical interviews in the morning. Two technical and one decomposition (see their site for what that is). Then they had a presentation called "Palantir 101" to describe what the company does. After we were supposed to have lunch with an engineer, but that turned into another decomposition. After that, I was told I made it to the "next round", though I assume the decision was made during Palantir 101 and the "next round" was also the decomposition I just did. Had an interview with the Hiring Manager that afternoon. Went home after that and got an answer within the next week.

Had a chat with HR and then a technical interview with an engineer. They gave some some quite normal leatcode type questions that I had to answer to continue to the next steps.